Genomic and functional potential of the immobilized microbial consortium MCSt-1 for wastewater treatment

Combined alkali-photocatalytic stimulation enables click microbial domestication for boosted ammonia nitrogen removal

Microbe-driven ammonia nitrogen removal plays a crucial role in the nitrogen cycle and wastewater treatment. However, the rational methods and mechanisms for boosting nitrogen conversion through microbial domestication are still limited. Herein, a combined alkali-photocatalytic stimulation strategy was developed to activate the Halomonas shizuishanensis DWK9 for efficient ammonia nitrogen removal. The strain DWK9 selected from saline-alkaline soil in Northwestern China possessed strong resistance to stress of saline-alkaline environment and free radicals, and was abundant in nitrogen conversion genes, thus is an ideal model for advanced microbial domestication. Bacterial in the combined alkali-photocatalytic stimulation group achieved a high ammonia nitrogen conversion rate of 67.5 %, 10 times outperforming the non-stimulated and single alkali/photocatalytic stimulation control groups. Morphology analysis revealed that the bacteria in the alkali-photocatalytic stimulated group formed a favorable structure for bioelectric transfer. Remarkably, the domesticated bacteria demonstrated improved electrochemical properties, including increased current capacity and lower overpotentials and impedance. Prokaryotic transcription genetic analysis together with qPCR analysis showed upregulation of denitrification-related metabolic pathway genes. A novel FAD dependent and NAD(P)H independent energy mode has been proposed. The universality and effectiveness of the as-developed combined alkali-photocatalytic microbial domestication strategy were further validated through indicator fish survival experiments. This work provides unprecedented degrees of freedom for the exploration of rational microbial engineering for optimized and controllable biogeochemical conversion.

Identification and genomic analysis of a thermophilic bacterial strain that reduces ammonia loss from composting

Ammonia loss is the most severe during the high-temperature stage (>50°C) of aerobic composting. Regulating ammonia volatilization during this period via thermophilic microbes can significantly improve the nitrogen content of compost and reduce air pollution due to ammonia loss. In this study, an ammonia-assimilating bacterial strain named LL-8 was screened out as having the strongest ammonia nitrogen conversion rate (32.7%) at high temperatures (50°C); it is able to significantly reduce 42.9% ammonia volatile loss in chicken manure composting when applied at a high-temperature stage. Phylogenetic analysis revealed that LL-8 was highly similar (>98%) with Priestia aryabhattai B8W22T and identified as Priestia aryabhatta. Genomic analyses indicated that the complete genome of LL-8 comprised 5,060,316 base pairs with a GC content of 32.7% and encoded 5,346 genes. Genes, such as gudB, rocG, glnA, gltA, and gltB, that enable bacteria to assimilate ammonium nitrogen were annotated in the LL-8 genome based on the comparison to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The results implied that the application of thermophilic ammonia-assimilating strain P. aryabhatta LL-8 would be a promising solution to reduce ammonia loss and mitigate air pollution of aerobic composting.IMPORTANCEAerobic composting is one of the essential ways to recycle organic waste, but its ammonia volatilization is severe and results in significant nitrogen loss, especially during the high-temperature period, which is also harmful to the environment. The application of thermophilic bacteria that can use ammonia as a nitrogen source at high temperatures is helpful to reduce the ammonia volatilization loss of composting. In this study, we screened and identified a bacteria strain called LL-8 with high temperature (50°C) resistance and strong ammonia-assimilating ability. It also revealed significant effects on decreasing ammonia volatile loss in composting. The whole-genome analysis revealed that LL-8 could utilize ammonium nitrogen by assimilation to decrease ammonia volatilization. Our work provides a theoretical basis for the application of this functional bacteria in aerobic composting to control nitrogen loss from ammonia volatilization.

Preparation of Newly Polymer-Coated Microbial Pellets and Their Adsorption and Degradation Properties for Oil-Containing Wastewater

Water is the lifeblood of everything on earth, nourishing and nurturing all forms of life, while also contributing to the development of civilization. However, with the rapid development of economic construction, especially the accelerated process of modern industrialization, the pollution of oily sewage is becoming increasingly serious, affecting the ecological balance and human health. The efficient elimination of pollutants in sewage is, therefore, particularly urgent. In this paper, a core-shell microbial reactor (MPFA@CNF-SA-AM) was fabricated by using nanocellulose and sodium alginate (SA) particles embedded with microorganisms as the core and lipophilic and hydrophobic fly ash as the outer shell layer. Compared with that of free microorganisms and cellulose and SA aerogel pellets loading with microorganisms (CNF-SA-AM), which has a degradation efficiency of 60.69 and 82.89%, respectively, the MPFA@CNF-SA-AM possesses a highest degradation efficiency of 90.60% within 240 h. So that this self-floating microbial reactor has selective adsorption properties to achieve oil-water separation in oily wastewater and high effective degradation of organic pollutants with low cost. The adsorption curves of MPFA@CNF-SA-AM for diesel and n-hexadecane were studied. The results showed that the adsorption follows the Freundlich model and is a multimolecular layer of physical adsorption. In addition, the degradation mechanism of diesel oil was studied by gas chromatography-mass spectrometry. The results showed that diesel oil was selectively adsorbed to the interior of MPFA@CNF-SA-AM, and it was degraded by enzymes in microorganisms into n-hexadecanol, n-hexadecaldehyde, and n-hexadecanoic acid in turn, and finally converted to water and carbon dioxide. Compared with existing oily wastewater treatment methods, this green and pollution-free dual-functional core-shell microbial reactor has the characteristics of easy preparation, high efficiency, flexibility, and large-scale degradation. It provides a new, effective green choice for oily wastewater purification and on-site oil spill accidents.

Sustainable management and valorization of biomass wastes using synthetic microbial consortia

In response to the persistent expansion of global resource demands, considerable attention has been directed toward the synthetic microbial consortia (SMC) within the domain of microbial engineering, aiming to address the sustainable management and valorization of biomass wastes. This comprehensive review systematically encapsulates the most recent advancements in research and technological applications concerning the utilization of SMC for biomass waste treatment. The construction strategies of SMC are briefly outlined, and the diverse applications of SMC in biomass wastes treatment are explored, with particular emphasis on its potential advantages in waste degradation, hazardous substances control, and high value-added products conversion. Finally, recommendations for the future development of SMC technology are proposed, and prospects for its sustainable application are discussed.

A novel hypothermic strain, Pseudomonas reactans WL20-3 with high nitrate removal from actual sewage, and its synergistic resistance mechanism for efficient nitrate removal at 4 °C

Nitrate can be well removed by bacteria at 25-30 °C. However, nitrate removal almost ceases at temperatures lower than 5 °C. In this study, a novel hypothermic strain, Pseudomonas reactans WL20-3 exhibited an excellent aerobic nitrate removal ability at 4 °C. It had high capability for the removal of nitrate, total dissolved nitrogen (TDN), and dissolved organic carbon (DOC) at 4 °C, achieving removal efficiencies of 100%, 87.91%, and 97.48%, respectively. The transcriptome analysis revealed all genes involved in the nitrate removal pathway were significantly up-regulated. Additionally, the up-regulation of ABC transporter genes and down-regulation of respiratory chain genes cooperated with the nitrate metabolism pathway to resist low-temperature stress. In actual sewage, inoculated with WL20-3, the nitrate removal efficiency was found to be 70.70%. Overall, these findings demonstrated the impressive capacity of the novel strain WL20-3 to remove nitrate and provided novel insights into the synergistic resistance mechanism of WL20-3 at low temperature.

Insights into nitrogen and phosphorus metabolic mechanisms of algal-bacterial aerobic granular sludge via metagenomics: Performance, microbial community and functional genes

Aiming to propose the potential mechanism for the enhancement of nitrogen (N) and phosphorus (P) removal of algal-bacterial aerobic granular sludge (A-AGS), metagenomic analysis was applied to identify the metabolic pathways. The results showed that chemical oxygen demand, ammonia nitrogen, total N, and total P removal of A-AGS could reach to 94.5%, 97.5%, 78.1%, and 88.5%, respectively. Algae enriched the content of extracellular polymeric substance, which significantly promoted the formation of A-AGS. Further investigations in functional genes suggested that nitrification process (amo, nxr, hao, etc.), denitrification process (nir, nap, nor, etc.), and polyphosphate accumulation (ppk, ppk2, etc.) were enhanced greatly in A-AGS. Notably, genus Thauera was the dominant source of functional genes, which penetrated both in N and P metabolism. The higher N and P removal performance in A-AGS could be attributed to synergistic effect between bacteria and microalgae, which may provide the basic for the application in wastewater treatment.

Performance and mechanism of nitrate removal by the aerobic denitrifying bacterium JI-2 with a strong autoaggregation capacity

Here, a new strain JI-2 of the strongly autoaggregating aerobic denitrifying bacteria was screened. The nitrate removal ability and autoaggregation mechanism of JI-2 were analyzed using the nitrogen balance and genomics technology. The nitrate removal rate was 27.05 mg N/(L·h) at pH 9.0 and C/N 8.0. The strain JI-2 removes nitrate via the aerobic denitrification and dissimilation pathways and removes ammonium via the assimilation pathway. 66.81 % nitrate was converted to cellular components under aerobic conditions. Complex nitrogen metabolism genes were detected in strain JI-2. C-di-GMP mediates the motility behavior of JI-2 by binding the FleQ and PilZ proteins, and regulating the expression of PslA. Furthermore, the mechanism of autoaggregation was verified by extracellular polymeric substance analysis. Meanwhile, the nitrate removal rates of strain JI-2 was 11.13-12.50 mg N/(L·h) in wastewater. Thus, strain JI-2 has good prospects for application in the treatment of nitrate wastewater.

Differential colonization and functioning of microbial community in response to phosphate levels

Microbes play a major role in phosphate cycling and regulate its availability in various environments. The metagenomic study highlights the microbial community divergence and interplay of phosphate metabolism functional genes in response to phosphate rich (100 mgL^-1), limiting (25 mgL^-1), and stressed (5 mgL^-1) conditions at lab-scale bioreactor. Total five core phyla were found responsive toward different phosphate (Pi) levels. However, major variations were observed in Proteobacteria and Actinobacteria with 33-81% and 5-56% relative abundance, respectively. Canonical correspondence analysis reflects the colonization of Sinorhizobium (0.8-4%), Mesorhizobium (1-4%), Rhizobium (0.5-3%) in rich condition whereas, Pseudomonas (1-2%), Rhodococcus (0.2-2%), Flavobacterium (0.2-1%) and Streptomyces (0.3-4%) colonized in limiting and stress condition. The functional profiling demonstrates that Pi limiting and stress condition subjected biomass were characterized by abundant PQQ-Glucose dehydrogenase, alkaline phosphatase, 5'-nucleotidase, and phospholipases C genes. The finding implies that the major abundant genera belonging to phosphate solubilization enriched in limiting/stressed conditions decide the functional turnover by modulating the metabolic flexibility for Pi cycling. The study gives a better insight into intrinsic ecological responsiveness mediated by microbial communities in different Pi conditions that would help to design the microbiome according to the soil phosphate condition. Furthermore, this information assists in sustainably maintaining the ecological balance by omitting excessive chemical fertilizers and eutrophication.

Optimizing biocatalytic potential of Dipodascus australiensis M-2 for degrading lignin under laboratory conditions

In present research, a potent fungal strain was isolated from paper mill effluent (black liquor) in order to investigate its potential for the biodegradation of lignin. Two step strategy was used to screen most efficient fungal strain having ability to growin MSM-black liquor medium and to degrade alkali lignin.The results of initial screening indicated that the strain M-2 produced comparatively higher ligninolytic zone on MSN agar plates supplemented with black liquor (BL) and alkali ligninase compared to the other isolates.The results of 18S rRNA gene sequencing revealed that strain M-2 showed ≥ 99% sequence homology with Dipodasceus australiansis.The process for the biodegradation of lignin was optimized using Taguchi Orthogonal Array design. Under optimized conditions of pH 9, 40 °C and 4% inoculum, a maximum of 89% lignin was degraded with 41% color reduction after 8 days of incubation period by Dipodasceus australiansis M-2. The pH and temperature were found to be significant terms with the p-values of 0.002 and 0.001 respectively. The laccase activity of the Dipodascus australiensis was found to be maximum of 1.511 U/mL. The HPLC analysis of lignin biodegradation indicated sharp transformation of peaks as compared to the control. Our results suggested that the strain Dipodascus australiensis M-2 possess excellent lignin degradation and color reduction capability and can be applied in waste treatment systems for pulp and paper mill effluent. In present work we are reporting first hand information regarding biodegradation of lignin by a potent strain of Dipodascus australiensis and statistical optimization of the bioprocess.

Nitrate removal by alkali-resistant Pseudomonas sp. XS-18 under aerobic conditions: Performance and mechanism

To improve poor nitrate removal by microorganisms under strong alkaline conditions, a new type of aerobic nitrification-reducing bacteria was isolated in this study. Using nitrogen balance and genome information, the capacity of Pseudomonas XS-18 to remove nitrate and the mechanism of alkali tolerance were analyzed. At pH 11.0, XS-18 could remove 12.17 mg N/(L·h) nitrate. At C/N ratios of 13.0 and 25 °C, nitrite and ammonia nitrogen were barely enriched. XS-18 could reduce nitrate through dissimilation and assimilation, and 21.74% and 77.39% of nitrate was converted into cellular components and organic nitrogen, respectively. Meanwhile, functional genes (nirBD, nasAB, gdhA, glnA, and gltBD) associated with nitrogen metabolism were determined. In addition, Na⁺/H⁺ antiporters (MnhACDEFG, PhaACDEFG, NhaCD and TrkAH) and a cell surface protein (SlpA) from the XS-18 genome, as well as compatible solutes that help stabilize intracellular pH, were also characterized. XS-18 possessed significant potential in alkaline wastewater treatment.